Steam boiler



Feb. 22, 1966 KE|J| OKANIWA 3,236,211

STEAM BOILER INVENTOR.

ifi/Jl O/(AA//WA BY Feb. 22, 1966 KEIJI oKANlWA STEAM BOILER 2 Sheets-Sheet 2 Filed July 20, 1962 INVENTOR.

Kfm @KAN/W4 United States Patent O 3,236,211 STEAM BOILER Keiji Okaniwa, Tsurumi-ku, Yokohama, Japan, assiguor to Yokoyama Kogyo Kahushiki Kaisha, Tokyo, Japan Filed July 20, 1962, Ser. No. 211,299 Claims priority, application Japan, July 26, 1961, 3dS/26,452; Aug. 12, 1961, 36/28,742 3 Claims. (Cl. 122-33) This invention relates to forced recirculation steam boilers. Steam boilers of conventional type in which a hot gas produced immediately `by the burning of fuel gives up its heat to feedwater for heating and evaporation thereof for the production of steam present difficult problems, one of which is a precipitation of organic and inorganic substances contained in the feedwater on heating surfaces or a formation of boiler scales, which results in a low efciency of the boiler and in some cases in explosions thereof. When a pure water made by means of ion-exchange resin is used as feedwater in order to eliminate said disadvantage, boiler explosion accidents can be prevented from occuring for a long time operation, but the result yis that the water used proves to be expensive.

Moreover, in order to avoid an overheating of tubes by concentation of solid ingredients in feedwater steam boilers of conventional type include a vapor-liquid separator serving to separate excess water after more water than steam to be produced is supplied in order to prevent the feedwater from increasing its concentation. If the load of such a boiler is changed, the feedwater quantity must be adjusted according to said load change. For example, in case of a sudden increase of the load the burning quantity of fuel and correspondingly the feedwater quantity at the same time are increased, but as there is a time lag in water flow in tubes, water is evaporated partially in the tubes and therefore overheating of the tubes, adhesion of boiler scales or boiler explosion accidents can be occurred.

With the foregoing in mind, one object of the present invention is to provide a steam boiler in which the first fluid circuit and the second fluid circuit are arranged, water circulating always through the former forcibly by means of a pump and the former having heating surface adapted to absorb heat generated by combustion gasses and heating surface adapted to give up the heat of the first fluid to the second fluid for the production of steam. As a consequence of this arrangement the disadvantages presented by forced recirculation steam boilers of conventional type can be eliminated.

According to this invention, as water is evaporated not or scarcely in the tubes of the first fluid circuit in spite of a considerable heat exchange at radiant heating surface and convective heating surface, a precipitation of solid substances and therefore a low heat conductivity of tubes by the adhesion of said precipitate on the inside surfaces of the tubes and overheating accidents in the first fluid circuit cannot occur. Therefore, the first fluid is not required to be highly pure, but can be relatively pure, in this case saturated water or vaporwater mixture with small vapor content being able to be used. lf boiler scales are brought about on the heating surfaces, they will be deposited only on the outsides of the tubes located in the second fluid circuit and therefore can easily be removed. Even in case ofoperation of a steam boiler according to this invention with boiler scales deposited on the outsides of the tubes there is no danger because the temperature of the heating surfaces never rises higher than that of hot water, heat transmitting medium. With this steam boiler, therefore, steam can be produced safely and efliciently even from conventional 3,236,211 Patented Feb. 22, 1966 ACe water, if the heating surfaces are only washed or cleaned mechanically at the time of starting.

According to this invention, the first fluid circulates always with a constant quantity of water and its temperature rises or falls according to an increased or decreased demand of the steam produced, more or less fuel then being burned, whereby the change of demand can be met. The flow in the first circuit is exceedingly stable and this circuit does not require a vapor-liquid separator.

These and other objects of the invention and the various features and details of the construction and operation thereof are hereinafter fully set forth and described with reference to the drawings, in which:

FIG. 1 is a longitudinal section through a two stage steam boiler constructed and arranged in one convenient form in accordance with this invention.

FIG. 2 shows a diagrammatic view of a preferred embodiment.

The two stage steam boiler shown in FIG. 1 comprises two fluid circuits of different kind, that is, the first fluid circuit I and the second fluid circuit II. The first fluid circuit I comprises in turn radiant heating surface 1, convective heating surface 2, surface 3 adapted to heat the second fluid and a pump 4 adapted to force the first fluid through the first fluid circuit, which form a closing flowing circuit. 5 denotes the circulating water pipe line and 6 the feedwater pipe line. The radiant heating surface 1 and the convective heating surface 2 com-- prises a single long tube and the radiant heating surface 1 is formed in a coil. One end of the heating surface 1 is connected with the heating surface 3 for the second fluid, which are arranged similarly in a coil 8 with a single long tube and the end of which is connected with the pump 4. The second fluid circuit II comprises an external casing 9, an internal shell 10, a feedwater inlet 11 and a steam outlet 12 and serves to produce steam to be supplied. 13 denotes the refractory walls.

The radiant heating surface 1 and the convective heating surface 2 of the first fluid circuit form a cylindrical furnace chamber 14 adapted for the burning of fluid fuel by means of a burner 15 in order to give up the heat of the heating gases to the first fluid. Then the heating gases flow through the combustion gas pass 16 and the flue 17 to the gas outlet 18. The first fluid circulating through the first fluid circuit flows through the convective and the radiant heating surface and gives up its heat to the second fluid at the heating surface 3 and then returns to the pump 4 with a relatively low temperature. The second fluid is supplied to the second fluid circuit by another pump (not shown). There are an upper vapor space and a liquid space in the second fluid circuit and the liquid level is so adjusted that the heating surface adapted to heat the second fluid is located below the liquid level. In addition the combustion gases contact with the internal shell part of the second fluid circuit, through which an additional heat exchange between the combustion gases and the second fluid takes place.

The first fluid circulates always repeatedly through the first fluid circuit, so that there is generally no necessity for supplying fresh water to the first fluid circuit, if the first fluid does not leak out at the circulating pump. When necessary, feedwater can be supplied to the first fluid circuit through the feedwater pipe line 6 by changing over a valve.

FIG. 2 has theoretically the same construction as that shown in FIG. 1. The first fluid supplied through a valve 36 is heated by a burner 37 located at the bottom of the furnace 38 when it flows through the heating surface 39 arranged in the furnace 38. The fluid thus heated is then delivered thraugh the connecting tube 41 to the heating surfaces 40 arranged in the second boiler 42. The second fluid is supplied from a feed valve 43, reheated in the econom-izer 44 arranged at the top of the furnace 38 and delivered through the connecting tube 45 to the second boiler 42. The steam produced in the second boiler 42 flows out through the steam outlet 46. 47 denotes a flue for combustion gases cooled by the economizer` 44 and 48 the peep window for Watching the state of boiler scales deposited on external surfaces of the heating tubes.` When necessary, the external surfaces of heating tubes where boiler scales are deposited are Washed or cleaned by mechanical shock and the sediments can be removed through a valve 49. In this case the steam boiler operates generally at a pressure of 50 kg./cm.2-l00 lig/cm.2 and a temperature of 250 C.-350 C. in therst fluidy circuit and at a pressure of 10 kg./cm.2 in the steam produced in the second fluid cir.

rst convectionv heating surface within said furnace anda second radiant heating surface Within said furnace and a third surface extending exteriorly from said furnace, a second fluid circuit surrounding said third surface of said first fluid circuit, means positioning said second circuit in heat exchange relationship with said furnace chamber, said rst fluid circuit being adapted to absorb heat from said combustion gases and to transfer heat to the fluid of said second uid circuit.

2. A vapor generator according to claim 1, wherein said second fluid circuit is formed in a jacket surrounding said furnace.

3. A vapor generator according to claim 1, further comprising pump means connected to said rst fluid circuit for circuating fluid therethrough.

References Cited by the Examiner UNITED STATESl PATENTS 1,040,688 10/1912 Jones 122-32 1,881,545 10/1932 Hartmann 122-33 1,959,286 5/1934 Grebe 122-33 1,987,182 1/1935 Dalen et al 122-33 2,008,528 7/ 1935 Warren 122-250 2,012,216 8/1935 Baumann 122-250 3,007,457 11/1961 Ospelt 1'22-37 FREDERICK L. MATTESON, JR., Primary Examiner.

FREDERICK KETTERER, KENNETH'W. SPRAGUE,

PERCY L. PATRICK, Examiners. 

1. A VAPOR GENERATOR COMPRISING MEANS DEFINING A FURNACE CHAMBER, MEANS FOR DELIVERING COMBUSTION GASES TO SAID FURNACE CHAMBER, A FIRST CLOSED FLUID CIRCUIT FORMED BY A SINGLE CONTINUOUS CLOSED TUBE, SAID TUBE FORMING A FIRST CONVECTION HEATING SURFACE WITHIN SAID SURFACE AND A SECOND RADIANT HEATING SURFACE WITHIN SAID FURNACE AND A THIRD SURFACE EXTENDING EXTERIORLY FROM SAID FURNACE, A SECOND FLUID CIRCUIT SURROUNDING SAID THIRD SURFACE OF 